1. Field of the Invention
The present invention relates to a clipping device for fixing two sheet members, such as two panels or a panel and a decorative material, to each other in a superposed state, and more particularly, to the clipping device in which the superposed and fixed state of the sheet members can be easily released.
Further, the present invention relates to a clipping device for fixing two sheet members such as two panels or a panel and a decorative material to each other in a superposed state, and more particularly, to the clipping device including a pin and a grommet which have been integrally molded of synthetic resin.
2. Description of the Related Art
A conventional clipping device of one type includes two components, namely, a pin and a grommet which are separately formed of synthetic resin, though not shown in a drawing specifically. The pin, the former, is in a columnar shape and provided with an engaging groove, an enlarging groove and a releasing groove which are formed on its outer peripheral face, in this order from a lower position, and set in such a manner that the engaging groove at the lower position and the releasing groove at an upper position have smaller groove diameters than the enlarging groove at a middle position. The grommet, the latter, has a cylindrical shape including a flange part and a body part. This body part is divided into a plurality of divisional leg portions interposing slits, and each of the divisional leg portions which can be enlarged in an opposed manner is provided, on its inner face, with an inwardly directed projection which is adapted to be engaged with the respective grooves of the aforesaid pin (Reference should be made to JP-B-5-10524, for example).
In order to superpose and fix two panels employing these pin and grommet, the pin is inserted into the grommet, as a first step, and then, the pin and the grommet are provisionally retained, by engaging the inwardly directed projections of the opposed divisional leg portions in the body part of the grommet with the engaging groove of the pin. Thereafter, the body part of the grommet is inserted into respective mounting holes in the panels, and an upper part of the pin which is projected from the flange part of the grommet is further pushed into the mounting holes. As the results, the inwardly directed projections of the divisional leg portions will be disengaged from the engaging groove, and will be engaged, this time, with the enlarging groove at the middle position which has the larger diameter, thus enabling the opposed divisional leg portions to be enlarged outwardly. In this manner, the two panels are fixed to each other in the superposed state.
On the other hand, in order to release the panels from the superposed and fixed state, the pin is further pushed in the same direction as the superposing and fixing direction. Then, the inwardly directed projections of the opposed divisional leg portions will be disengaged from the enlarging groove, and will be engaged, this time, with the releasing groove at the upper position which has the smaller diameter. With this motion, the divisional leg portions will be automatically released from the enlarged state, and return to their original free state, thereby to release the clamping state with respect to the panels. Therefore, the superposed and fixed state of the panels can be easily released, by pulling out, thereafter, the grommet together with the pin from the mounting holes.
As described above, the conventional clipping device has had such an advantage that the superposed and fixed state between the panels can be easily released without damaging the pin and the grommet, because a so-called push-push system has been employed. However, in order to reliably engage the inwardly directed projections of the divisional leg portions with the releasing groove of the pin for this purpose, it is necessary to provide means for preventing the pin from being excessively pushed into an interior of the grommet. Although such means have been provided between the pin and the grommet also in the conventional clipping device, under the circumstances that the pin and the grommet have been separately molded of synthetic resin from the beginning, it has been necessary to pre-assemble them, by inserting the pin into the interior of the grommet in advance by hand or by an assembling machine, after molding. Accordingly, the clipping device has been unable to be manufactured at low cost. It has been also considered to integrally mold the pin and the grommet, and thereafter, to pre-assemble them by inserting the pin into the interior of the grommet. However, in case where the pin and the grommet have been integrally molded, even though it has been intended to provide means for preventing the pin from being excessively inserted into the grommet, for example, a convex part for receiving a stepped part of the pin, on the body part of the grommet, it has been technically difficult to provide the convex part, since the pin which has been integrally molded so as to cover an upper part of an opening in the grommet may become an obstacle. Even though the convex part having a small protruding amount can be provided, it has been difficult for this convex part to reliably prevent an excessive insertion of the pin with a sufficient strength.
Further, as conventional clipping devices of one type, a number of the clipping devices having various structures have been heretofore proposed. Essentially, any of them is an integrally molded product of synthetic resin, and includes two components, namely, a pin in a columnar shape and a grommet in a cylindrical shape. The pin, the former has a head part, and a shaft part adapted to be inserted into a body part of the grommet which will be described below. The grommet, the latter, has a flange part, and a body part which can be enlarged. The pin and the grommet are integrally coupled by means of small bridge pieces which can be torn off (Reference should be made to JP-B-44-7768, JP-A-61-42212, JP-A-2003-172327 and JP-A-2003-247518, for example).
For this reason, it is needless to say that the pin and the grommet are easy to be handled in the conventional clipping device, because they have been integrally molded from the beginning of molding. Especially in case where they are assembled into a provisionally retained state, the aforesaid small bridge pieces will be torn off inside or outside a molding cavity, and in this state, the shaft part of the pin will be forcibly inserted into the body part of the grommet, whereby the pin and the grommet can be immediately assembled into the provisionally retained state. Therefore, the clipping device has such an advantage that an assembling work can be extremely simplified, and cost for a mold for molding work can be reduced.
As described above, the conventional clipping device which has been integrally molded has had a remarkable advantage that the assembling work can be simplified as compared with the clipping device which has been separately molded. On the contrary, in case of forcibly tearing the small bridge pieces in order to obtain the provisionally retained state between the pin and the grommet, there has been such anxiety that, in case where the tearing action is conducted on a side of the pin, the small bridge pieces remaining on a side of the grommet become serious obstacles, on occasion of inserting the shaft part of the pin completely into the body part of the grommet for enlarging the body part of the grommet outwardly, and the shaft part of the pin becomes difficult to be smoothly inserted into the body part of the grommet.